Filter elements and additives therefor



United States Patent C 3,417,758 FILTER ELEMENTS AND ADDITIVES THEREFOR Cephas H. Sloan and Bobby J. Sublett, Kingsport, Tenn, assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Jan. 15, 1965, Ser. No. 425,920 2 laims. (Cl. 131-266) ABSTRACT OF THE DISCLOSURE A selective tobacco smoke filter element containing a water-soluble, weak basic inorganic salt which is capable of chemically reacting with and rendering harmless substantially all hydrogen cyanide vapors contained in the tobacco smoke passing through the filter elements. The organic salt is selected from the group consisting of sodium phosphite and potassium phosphite.

This invention relates to filters that will remove hydrogen cyanide from smoke. More particularly it relates to filter elements containing additives which will effectively neutralize the hydrogen cyanide normally encountered in tobacco smoke.

In US. Patent 2,940,456 our co-worker Touey disclosed use of calcium and magnesium carbonates to remove particulate matter commonly referred to as tars. Since issuance of said patent a need has developed for removal from tobacco smoke of certain other substances not removable by said carbonates. Such substances include hydrogen cyanide. After extended investigation we have found a group of additives that will remove hydrogen cyanide from tobacco smoke when applied to the tow of tobacco smoke filters.

One object of this invention is to provide a filter element that will remove a considerable amount of hydrogen cyanide from the vapor portion of tobacco smoke. Another object is to provide a method of increasing the filtration efficiency of tobacco smoke filter elements. Further objects will appear hereinafter.

In its broader aspects our invention involves applying to a filter tow such as acetate tow a water-soluble inorganic salt of a Group Ia element. Preferred salts are the carbonates, and phosphites of sodium and potassium. The salts are preferably finely divided. The preferred particle size is such that the particles will pass through a 100-mesh screen (U.S. S. Sieve). The water-soluble inorganic salt may be applied by sifting, dusting, shaking, or from a water solution or plasticizer dispersion. It may also be applied by spraying or rolling on the tow. More than one salt may be used as a mixture if desired.

A preferred tow on which the additives of this invention may be used is crimped continuous filament cellulose acetate tow, preferably of a denier per filament of about 1.6 to 10.

The water-soluble inorganic salt may be applied to the tow in the amount of from 1 to 30% by weight, the preferred amount being 2 to by weight of the filter element prepared from the tow to which additive is applied. By uniform application to the surface of the tow the salt is enabled to take advantage of the large surface area which provides the contact necessary for hydrogen cyanide removal by neutralization.

According to one embodiment of our invention the crimped tow is spread out to a width of 10-20 inches or so and a plasticizer for the tow, containing 10 to 50% by weight of the water-soluble inorganic salt dispersed therein, applied by padding the tow with rollers. The tow is then compacted, wrapped with paper to form a rod, and allowed to stand until firm. Addition of the plasticizer dispersion helps add rigidity to the resulting rod and leaves the salt evenly distributed on the surface of the tow. After the rod becomes firm, it may be cut into any desired length and used either alone as a filter or in combination with other filters to make a dual or multiple filter.

The following example is illustrative of our invention.

Example I A 170-mm. portion of 3 denier/ filament crimped cellulose acetate filter tow which had 20,000 filaments and Weighed approximately 1 gram was spread out to a width of 15 inches. A blend of 30 parts diethylene glycol, 60 parts triacetin, and 20 parts sodium carbonate (ZOO-meshv powder) was padded on the opened tow until mg. of the total mixture was added. The tow was then recompacted and wrapped with a paper tape to form a filter rod with a circumference of 25 mm. The rod was allowed to stand until firm and was then cut into 17-min. segments which contained approximately 2 mg. of sodium carbonate. The 17-min. segments were attached to a kingsize cigarette by means of a cellophane tape, and the cigarette smoked on an automatic smoking device. The vapors which passed through the filter were collected and analyzed for hydrogen cyanide by a spectrophotometric method. The vapors from a king-size cigarette which did not have a filter were collected, analyzed in the same manner, and the two analyses were compared. The cigarette without filter delivered 138 ,ug. of hydrogen cyanide, and the cigarette containing the treated cellulose acetate filter delivered only 23 g. of hydrogen cyanide.

We claim:

1. A selective tobacco smoke filter element comprising a plurality of cellulose ester fibers and containing from 1 to 30% by weight of said element of a water soluble, weak base inorganic salt capable of chemically reacting with and selectively rendering harmless hydrogen cyanide vapors contained in the tobacco smoke passing through the filter element, the water soluble inorganic salt being selected from the group consisting of sodium phosphite and potassium phosphite.

2. A selective tobacco smoke filter element according to claim 1 wherein said salt is present in an amount of from 2 to 10% by weight of said element.

References Cited UNITED STATES PATENTS 2,832,351 4/1958 Hale 131-266 X 3,368,566 2/1968 Avedikian 131-265 X 3,320,961 5/1967 Hughes et al. v 131-267 2,172,946 9/ 1939 Sutter 131-265 3,101,723 8/1963 Seligrnan et a1. 131-269 X FOREIGN PATENTS 86,246 11/ 1921 Austria. 760,772 11/ 1956 Great Britain.

908,185 10/ 1962 GreatBritain.

SAMUEL KOREN, Primary Examiner.

DENNIS I. DONOHUE, Assistant Examiner.

US. Cl. X.R. 

